Changes in pH and acidity during the acetic fermentation of H. erinaceus wine are shown in Fig. 2(b). The pH decreased from 3.02 to 2.65 over 9 days of acetic fermentation. The acidity increased gradually during acetic fermentation and after 9 days reached 4.09%, which is in the same range as brewed vinegar, cider vinegar, brown rice vinegar and persimmon vinegar